JDBC Connection Example in Java

Introduction

JDBC (Java Database Connectivity) is the standard API for connecting Java applications to relational databases such as MySQL, PostgreSQL and Oracle.

Prerequisites

• A running database server
• JDBC driver JAR on the classpath
• Valid URL, username and password

Example Program

import java.sql.*;

public class JdbcConnectionDemo {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/testdb";
        String user = "root";
        String password = "password";

        try (Connection conn = DriverManager.getConnection(url, user, password);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT id, name FROM users")) {

            System.out.println("Connected successfully");
            System.out.println("ID\tNAME");
            System.out.println("----------------");

            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                System.out.println(id + "\t" + name);
            }
        } catch (SQLException e) {
            System.err.println("Database error: " + e.getMessage());
        }
    }
}

Sample Output

Connected successfully
ID	NAME
----------------
1	Alice
2	Bob
3	Charlie

Best Practices

• Use PreparedStatement with ? placeholders for dynamic values.
• Never embed raw user input in SQL strings.
• Store credentials in environment variables or secure config, not source code.

Common Mistakes

• Forgetting the JDBC driver on the classpath (ClassNotFoundException).
• Not closing connections in older code — always use try-with-resources.

How It Works

Here is a step-by-step walkthrough of how the Java program for JDBC Connection Example in Java runs, line by line:

1. public class JdbcConnectionDemo { — performs part of the program’s logic.
2. public static void main(String[] args) { — defines a function used by the program.
3. String url = "jdbc:mysql://localhost:3306/testdb"; — declares or assigns a value the program uses.
4. String user = "root"; — declares or assigns a value the program uses.
5. String password = "password"; — declares or assigns a value the program uses.
6. try (Connection conn = DriverManager.getConnection(url, user, password); — declares or assigns a value the program uses.
7. Statement stmt = conn.createStatement(); — declares or assigns a value the program uses.
8. ResultSet rs = stmt.executeQuery("SELECT id, name FROM users")) { — declares or assigns a value the program uses.

After running it, compare your console output with the Sample Output above. Try changing the values and re-running the program to see how the result changes — experimenting is the fastest way to understand the logic.